The enzyme known as catalase (EC 1.11.1.6) catalyzes the decomposition of hydrogen peroxide into water and molecular oxygen. In the cell, hydrogen peroxide is produced as a by-product of aerobic metabolism and has the potential to damage a variety of macromolecules including DNA (Brawn and Fridovich, Arch. Biochem. Biophys. 206: 414-419, 1981). Catalase is induced as a defense against H.sub.2 O.sub.2 -mediated damage.
The enzyme has been proposed for many commercial uses. In general terms, it can be used in any situation in which it is desired to remove residual hydrogen peroxide from a system to which hydrogen peroxide has been added, e.g., for pasteurization or bleaching. One such example is the use of catalase in the textile industry for the removal of hydrogen peroxide from fabric which is bleached by an alkaline hydrogen peroxide treatment before dyeing. A similar application is its use in pulp bleaching. Catalase can also be used in the removal of hydrogen peroxide from contact lenses after hydrogen peroxide disinfection.
A number of different types of catalases have been isolated and identified, from animal, plant and microbial sources. In particular a number of filamentous fungal catalases have been found. Those which have been characterized consist of four polypeptide subunits, each having a molecular weight of 80,000 to 97,000 and contain one heme prosthetic group per subunit. For example, catalase has been characterized from Penicillium (Vainshtein et al., J. Mol. Biol. 188: 63-72, 1986), from Neurospora (Jacob and Orme-Johnson, Biochemistry 18: 2967-2975, 1979), from Acremonium and Thermoascus (JP 5153975) and from Aspergillus (Fowler et al., Mol. Microbiol. 9: 989-998, 1993). The genes encoding certain of these catalases have also been isolated, and recombinant expression achieved (WO 93/17721, Wo 93/18166; JP 3103182; JP 1086879; JP 63017693); An extremely stable catalase, which retains activity at higher temperature and pH than other known catalases, has been isolated from strains of Scytalidium and Humicola (WO 92/17571). These properties make the Scytalidium/Humicola catalases particularly effective in the removal of residual peroxide in textile applications. However, recombinant production of this enzyme has not heretofore been accomplished. The present invention provides the gene encoding the Scytalidium catalase and a method for recombinant expression of same.